A very good eye. I hadn't noticed that myself. I've compared it to all my other SMLE's. My minty FTR's of course have nice sharp bayonet boss shoulders, probably 'cause they've never been used. My other pre-WWI and WWI issue beasties have more rounded shoulders presumably from use. This one is the most rounded, slightly more on the side of the 5 than the side of the 6. There is a trace of a scuff there too, so I wonder if it might have gotten "dinged" at one point a long time ago and needed some buffing to smooth it out. The patina on it is old. The sides are straight, and it fits a bayonet quite well still. Interesting.

Cheers

Ed